Midway Atriums

PREVIOUS SITUATION

The complex’s existing HVAC system consisted of 24 Carrier indoor 30-ton air-cooled DX self-contained units with high velocity coils, with 12,000 CFM variable air volume and 1.5” wg, plus 24 outdoor condensers.

The existing system was well past its useful life and was extremely unreliable. Repairs were very difficult because components were obsolete and hard to find. Maintaining comfortable temperatures was becoming nearly impossible. While the system urgently needed replacing, the buildings’ mechanical rooms had been built around the original equipment, making it extremely challenging to demo the old equipment and bring new equipment in.

DESIRED SITUATION

The occupancy rate for the entire complex was about 80%, with two of the three buildings fully occupied. The client wanted a complete replacement of the HVAC system with as little physical impact to the buildings and tenants as possible.

The primary goal of the system replacement was to increase tenants’ comfort by ensuring reliable cooling and improving humidity levels in the buildings. Improvements to energy efficiency were also desired.

SOLUTION PROVIDED BY APPLIED CLIMATE

Applied Climate drew on its national product portfolio to develop a custom solution that satisfied the system design requirements and that could be knocked down into smaller components to fit the buildings’ standard doors and elevators and existing mechanical rooms. Applied Climate Solutions installed new Dunham Bush DB Aire III air-cooled self-contained CRAC units.

Each had a factory-provided vertical flow discharge plenum and two variable volume EC motors controlled via a factory-mounted and factory-programmed BACnet MSTP DDC controller with a color touchscreen graphical user interface, and a dual compressor with a variable speed compressor on circuit 1.

The dimensions of each unit were 35.5” x 100.6” x 102.5”. New refrigerant risers were installed and fully insulated, together with factory-engineered refrigerant accessories and oil traps, plus factory-installed oil separators. In addition, the outside air hoods were replaced with new O/A hoods.

Minimizing downtime during installation was critical. The work was done over a series of weekends, with demo starting on Thursdays and new system start-up taking place on Sunday night before tenants returned to work on Monday morning. In addition, to reduce physical disruption to the building and tenants, the old equipment was fully knocked down in-field for easy fit into standard doors and standard elevators.

Replacing the old system’s constant speed fans and constant speed compressors with variable speed fans and compressors has yielded greater energy efficiency, reducing energy consumption. In addition, the new system has improved discharge temperature, discharge pressure control, and humidity levels, resulting in increased comfort for tenants.